Search

Bovine adrenal chromaffin cells share many characteristics with neurons and are often used as a simple model system to study ion channels and neurotransmitter release. We infected bovine adrenal chromaffin cells with a replication deficient adenovirus that induces expression of the common reporters beta-galactosidase and Green Fluorescent Protein via a bicistronic sequence. In perforated-patch recordings performed 48-h postinfection, peak calcium currents were reduced 32%, primarily due to loss of omega-conotoxin-GVIA-sensitive current. In contrast, sodium currents were increased 17%. Exocytosis, detected as an increase in membrane capacitance immediately after a single step depolarization, was reduced in proportion to the decrease in calcium influx. However, capacitance continued to increase for seconds after the depolarization. The amplitude of this poststimulus drift, or asynchronous exocytosis, was approximately three times that which occurred in a small fraction of control cells. Exocytosis evoked by repetitive stimulation with a train of brief depolarizations was increased 50%. Intracellular calcium levels measured during and after stimulation were lower, not higher, in adenovirus-infected cells. Electroporated cells showed reduced calcium currents but no enhancement of exocytosis. Cells infected with UV-irradiated virus showed reduced calcium currents and enhancement of exocytosis, but the changes were smaller than those caused by intact virus. Our results are consistent with the idea that adenovirus capsid and adenoviral DNA contribute to a Ca2+ influx- and [Ca2+]i-independent enhancement of exocytosis in bovine chromaffin cells.

We examined the mechanism underlying increased quantal content after block of activity at the mouse neuromuscular junction in vivo. We found that, when quantal content was measured in solution containing normal extracellular calcium, block of activity had no effect on either quantal content or the response to repetitive stimulation. However, when quantal content was measured in low extracellular calcium, there was a large increase in quantal content after block of activity. The increase in quantal content was accompanied by increased depression during repetitive stimulation. The explanation for these findings was that there was a shift in the calcium dependence of release after block of activity that manifested as an increase in probability of release in low extracellular calcium. Block of presynaptic P/Q channels eliminated the increase in probability of release. We propose that activity-dependent regulation of presynaptic calcium entry may contribute to homeostatic regulation of quantal content.

In this work, the SO2 removal performances of the aluminum- and the magnesium-modified carbide slags fabricated by the combustion synthesis from CO2 capture cycles at the calcium looping conditions were investigated in a thermogravimetric analyzer and a dual fixed-bed reactor. The effects of sulfation temperature, number of CO2 capture cycles and calcination condition on the SO2 removal performances of Al- and Mg-modified carbide slags experienced the multiple CO2 capture cycles were studied. The sulfation temperature in the range of 800–950 °C shows a little effect on SO2 removal capacities of Al- and Mg-modified carbide slags experienced the multiple CO2 capture cycles. As the number of CO2 capture cycles increases, the sulfation conversions of the original and modified carbide slags decrease rapidly. However, Al- and Mg-modified carbide slags possess obviously higher SO2 removal capacity and cyclic stability than original carbide slag due to the good supports Ca3Al2O6 and MgO, respectively. And the larger surface areas and volumes of pores in 5–20 nm in diameter of Al- and Mg-modified carbide slags promote the higher SO2 removal capacity than original carbide slag. The modified carbide slag shows higher sintering resistance in high concentration of steam calcination condition during the CO2 capture cycles, compared with high concentration of CO2 calcination condition. Therefore, Al- and Mg-modified carbide slags from CO2 capture cycles based on calcium looping calcined under high steam concentration achieve SO2 removal capacities. [ABSTRACT FROM AUTHOR]

CaO/Ca(OH)2 thermochemical heat storage (THS) technology is considered to be one of the most promising technologies for large‐scale solar energy storage. However, the THS performance of raw CaO‐based materials decreases during multiple cycles. In this work, CaO derived from calcium acetate (Ac‐CaO) is prepared and applied to a coupled system that achieved simultaneous CaO/Ca(OH)2 THS and CO2 capture. The CO2 capture and THS performances of Ac‐CaO are always higher than those of calcined limestone owing to the preferable pore structure, whereas Ac‐CaO exhibits decreasing CO2 capture and THS performance resulting from sintering and the formation of CaCO3 from CaO or Ca(OH)2 with ambient CO2 during air cooling, respectively. In the coupled CaO/Ca(OH)2 THS and CO2 capture system, Ac‐CaO is subjected to 10 CO2 capture cycles, 30 THS cycles, 1 CO2 capture cycle, 10 THS cycles, 1 CO2 capture cycle, and 10 THS cycles sequentially. The hydration and dehydration conversions of Ac‐CaO in the 31st THS cycle reach 91.7 and 93.6%, respectively, which are 1.6 and 1.6 times higher than those recorded prior to the 11th CO2 capture cycle owing to the decomposition of CaCO3 during calcination. The carbonation conversion of Ac‐CaO achieves 89.9% in the 11th CO2 capture cycle, which is 22.3% higher than that recorded prior to the 10 THS cycles owing to reactivation from the hydration process during THS. The CO2 capture and CaO/Ca(OH)2 THS processes are enhanced in the coupled system using Ac‐CaO; therefore, the coupled system appears promising for CaO/Ca(OH)2 THS and CO2 capture. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• Mn/Mg-copromoted carbide slag is produced using dolomite and trace Mn(NO 3) 2. • MgO acts as skeleton and Mn acts as an electron-transfer promoter for CO 2 capture. • The optimal MnO 2 content in the Mn/Mg-copromoted carbide slag is 0.75 %. • MnO 2 positively affects the diffusion-controlled stage of carbonation. • The optimal Mn/Mg-copromoted carbide slag captures 0.52 g CO 2 /g after 10 cycles. Loss-in-capacity of carbide slag in CO 2 capture restricts the development of industrial wastes in calcium looping technology. In this work, a novel Mn/Mg-copromoted carbide slag was prepared using carbide slag, dolomite and trace Mn(NO 3) 2 additive. Experimental tests were carried out in the fixed-bed reactor to evaluate how the preparation and the reaction conditions influenced the CO 2 capture performance of Mn/Mg-copromoted carbide slag during calcination/carbonation cycles. Results show that MgO diminishes the sintering of synthetic sorbents. The optimal Mn/Mg-copromoted carbide slag (mass ratio of CaO:MgO:MnO 2 = 89:10:1) exhibits the highest CO 2 capture capacity of 0.52 g/g after 10 cycles under the severe calcination condition (100 % CO 2 , 950 °C) and the wet carbonation condition (15 % CO 2 /20 % steam/N 2), which is 1.7 times as high as that of untreated carbide slag. MnO 2 positively affects the slow carbonation stage by enhancing the electron transfer between CaO and CO 2. Observations of the morphology of Mn/Mg-copromoted carbide slag indicate that the stabilized CO 2 capture performance is mainly attributed to porous structure, MgO as the skeleton and MnO 2 as an electron-transfer promoter. [ABSTRACT FROM AUTHOR]

Herein, the novel CaO/MgO CO2 sorbent was fabricated from carbide slag and dolomite by the combustion method during the calcium looping process. The carbide slag is a precursor of CaO, and dolomite is a precursor of both MgO and CaO. The effects of the mass ratio of the carbide slag to dolomite, calcination conditions and presence of steam during carbonation on the CO2 capture performance of the novel CaO/MgO sorbent were studied during the calcium looping cycles. When the mass ratio of the carbide slag to dolomite was 74 : 26, the resulting CaO/MgO sorbent having the mass ratio of CaO to MgO = 90 : 10 achieved highest CO2 capture capacity that was retained at 0.52 g g−1 after 20 cycles (carbonation in 15% CO2/85% N2 at 700 °C for 20 min; calcination in 100% N2 at 850 °C for 10 min), which was higher than those of the carbide slag and other reported CaO/MgO sorbents prepared from analytical reagents. Compared with that of the sample calcined under pure CO2 at 950 °C, the CO2 capture capacity of the CaO/MgO sorbent calcined in pure steam at 800 °C is apparently higher. This novel CaO/MgO sorbent fabricated from industrial waste and dolomite exhibits a more porous microstructure, which is promising for the calcium looping process for CO2 capture. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A bifunctional system integrating with CO 2 capture and heat storage is proposed. • Original carbide slag can be used in CaO/Ca(OH) 2 thermochemical heat storage process. • High Cl content results in low cyclic CO 2 capture capacity of carbide slag. • Hydration performance of carbide slag with Cl is improved after CO 2 capture cycles. • CaO after CO 2 capture cycles is promising to be used for heat storage. Abstract Carbide slag is an industrial waste generated from ethylene gas production in chlor-alkali plants. Here, a novel system coupling calcium looping and CaO/Ca(OH) 2 thermochemical heat storage using carbide slag were proposed to simultaneously capture CO 2 and store heat. For CaO/Ca(OH) 2 thermochemical heat storage, the hydration/dehydration performance of original carbide slag and carbide slag that experienced calcium looping cycles for CO 2 capture was investigated. The performances of the two types of carbide slag with and without chlorine were compared. The dehydration conversions of carbide slag improved with the increase of dehydration temperature. The chlorine content has no apparent effect on the hydration/dehydration performance of original carbide slag. However, for CO 2 capture, carbide slag with high chlorine content shows lower carbonation conversion than that of carbide slag without chlorine. The hydration/dehydration conversions of carbide slag that experienced CO 2 capture cycles are lower than those of original carbide slag. For carbide slag with chlorine, the hydration conversion can be improved by more than one CO 2 capture cycle. Therefore, carbide slag that experienced various CO 2 capture cycles is still suitable to be used in CaO/Ca(OH) 2 thermochemical heat storage although calcium looping has an adverse effect on the hydration/dehydration performance of carbide slag. [ABSTRACT FROM AUTHOR]

Calcium looping technology is considered to be one of the most feasible techniques for CO 2 capture. A low-cost and easy method was proposed to improve the cyclic CO 2 capture capacity of the limestone by discontinuously adding hydrogen chloride (HCl) in the carbonation step in some cycles rather than in the each cycle at the calcium looping conditions. The effects of the discontinuous addition of HCl under the various conditions on the CO 2 capture performance of the limestone at the calcium looping conditions were investigated in a dual fixed-bed reactor. The results show that HCl addition during the initial several cycles leads to the formation of CaClOH and the moderate CaClOH in the carbonation product is favorable to CO 2 capture by the limestone. HCl addition only in the initial 3 cycles changes the effect of carbonation temperature on CO 2 capture by the limestone. The optimum carbonation temperature for the limestone with the addition of HCl is 700 °C in the range of 650–750 °C. Higher CO 2 volume fraction in the carbonation leads to lower CO 2 capture capacity of the limestone with the addition of HCl only in the initial 3 cycles. The discontinuous addition of HCl during the various cycles significantly enhances the CO 2 capture capacity of the limestone. HCl addition in the carbonation stage during only the initial cycles improves the pore structure of the calcined limestone and retards the fusion of CaO grains, which contributes to high CO 2 capture capacity of the sorbent in the multiple cycles. [ABSTRACT FROM AUTHOR]

• In-situ conversion mechanism of captured CO 2 by CaO in H 2 was studied by DFT theory. • Detailed reaction paths of direct reduction of CaCO 3 to form CO and CaO by H 2. • The presence of H 2 reduces a 0.35 eV in the energy barrier for CaO generation. • H 2 addition leads to reduced C O orbital overlap and electron cloud disturbances. In-situ conversion of the captured CO 2 by CaO to CO is realized by using renewable H 2 in the calcination stage of calcium looping process, which effectively reduces the decomposition temperature of CaCO 3 and alleviates the sintering of CaO. However, the mechanism for this reaction is unclear which is difficult to determine just by experimental methods. In this work, the reaction mechanism for in-situ conversion of captured CO 2 by CaO to CO in presence of H 2 during calcium looping process was investigated by density function theory (DFT) analysis. The CaCO 3 direct decomposition was compared to clarify the effect of H 2 on CaO regeneration. The electron differential densities (EDD) and partial density of states (PDOS) for HCO 3 * and CO 3 * models were also compared. The results show the detailed reaction pathway for in-situ conversion of the capture CO 2 by CaO in presence of H 2 in the calcination stage of CaCO 3. H 2 is adsorbed on the CaCO 3 surface to form OH*, CO 2 *and HCO 3 *. CO 2 * further is decomposed into CO and O*. HCO 3 * is decomposed into CO 2 and OH*. Then, two OH* are attracted to each other to form H 2 O and O*. The CO 3 * hydrogenation is the rate control step in this reaction with energy barrier of 3.12 eV. The presence of H 2 causes a 0.35 eV reduction in the energy barrier for CaO generation on CaCO 3 surface. The overlap of C O orbitals and the disturbance of electron clouds around O atom all confirm that the addition of H 2 makes C and O atoms in HCO 3 * have small interaction energy. The DFT calculations reinforce the possible mechanism of in-situ conversion of the captured CO 2 by CaO in presence of H 2 during calcium looping process. [ABSTRACT FROM AUTHOR]

The effects of reaction temperature, fluidization number, particle size and number of calcination/carbonation cycles on attrition and CO 2 uptake characteristics of carbide slag during the calcium looping cycles were investigated in a fluidized bed reactor. The attrition behaviors of carbide slag and limestone were also compared. Higher calcination temperature in 850–950 °C improves the attrition rate of carbide slag particles. CO 2 uptake capacity of carbide slag increases with fluidization number in carbonation. As fluidization number increases from 7 to 15, the mean diameter of carbide slag particles decreases by 4% and the attrition rate increases by 1.7 times after 10 cycles. Smaller particles show higher attrition resistance during the cycles. The breakage of larger particles of limestone is more severe than that of carbide slag during the cycles. CO 2 uptake capacity of the carbide slag is practically identical to that of limestone in short carbonation duration (e.g. 5 min) during the cycles. The effects of the number of calcination/carbonation cycles on the mean diameter and the attrition rate of carbide slag are less than those of limestone. Carbide slag possesses higher attrition resistance than limestone during the multiple CO 2 capture cycles. [ABSTRACT FROM AUTHOR]

Accurately evaluating the rate at which calcium-based alkaline industrial derived wastes (CAIDW) dissolve is very important in the design and development of CAIDW-type wet flue gas desulfurization plants. The dissolution characteristics of alkaline slag (AS) and salt mud (SM) have been studied using pH stat method, and the effects of various parameters such as reaction temperature, sorbent particle size and solution acidity are studied to determine the dissolution kinetics of AS and SM. The production process of CAIDW presents high influence on its dissolution performance in acidic conditions. The kinetics analysis based on the modified shrinking core model (MSCM) indicates that AS dissolution kinetics, which is accompanied by surface reaction control, follows the film diffusion, and the activation energies of the two steps are 4.62 ± 0.8 and 36.34 ± 3.1 kJ/mol, respectively. Meanwhile, the SM dissolution obeys the surface reaction model with the activation energy of 9.69 ± 1.9 kJ/mol. [ABSTRACT FROM AUTHOR]

Highlights: [•] HCl improves CO2 capture capacity of limestone in the previous a dozen cycles. [•] HCl sharply decreases limestone reactivity after a dozen cycles. [•] HCl intensifies effects of carbonation and calcination temperature on CO2 capture. [•] HCl enlarges effects of particle size on CO2 capture. [•] HCl severely aggravates the sintering of limestone after a dozen cycles. [ABSTRACT FROM AUTHOR]

Abstract: Lime mud (LM), a solid waste that results from the causticization reaction in alkali recycling process of paper manufacture industry, was utilized as CO2 sorbent in calcium looping process in this study. The carbonation behavior of LM in the calcination/carbonation cycles was investigated in a dual fixed-bed reactor and a thermo-gravimetric analyzer. The results show that the carbonation conversions of LM are lower than those of limestone at the same reaction conditions. It attributes to the high chlorine content in LM which leads to more pronounced sintering and decreases the CO2 capture performance of LM. A pre-wash process was employed to decrease the chlorine content in LM. Based on an overall consideration of various factors, the pre-wash process is effective enough if the Cl/Ca molar ratio in LM is smaller than 1:100. Pre-washed lime mud (PLM) achieves higher carbonation rates and carbonation conversions, compared with LM. When calcined at 850°C and carbonated at 700°C, the carbonation conversion of PLM maintains at 36% after 100cycles, which is 1.8 and 4.8 times as high as LM and limestone after the same number of cycles, respectively. The pore volume and surface area of calcined PLM were greater than those of calcined LM after the same number of cycles, especially the volume of the pores in the range of 10–100nm in diameter. That is the reason why PLM exhibits higher CO2 capture capacity than LM in the multiple calcination/carbonation cycles. The carbonation conversions of LM and PLM are further enhanced by hydration of their calcines. [Copyright &y& Elsevier]

Abstract: The effects of manganese salts including Mn(NO3)2 and MnCO3 on CO2 capture performance of calcium-based sorbent during cyclic calcination/carbonation reactions were investigated. Mn(NO3)2 and MnCO3 were added by wet impregnation method. The cyclic CO2 capture capacities of Mn(NO3)2-doped CaCO3, MnCO3-doped CaCO3 and original CaCO3 were studied in a twin fixed-bed reactor and a thermo-gravimetric analyzer (TGA), respectively. The results show that the addition of manganese salts improves the cyclic carbonation conversions of CaCO3 except the previous cycles. When the Mn/Ca molar ratios are 1/100 for Mn(NO3)2-doped CaCO3 and 1.5/100 for MnCO3-doped CaCO3, the highest carbonation conversions are achieved respectively. The carbonation temperature of 700–720°C is beneficial to CO2 capture of Mn-doped CaCO3. The residual carbonation conversions of Mn(NO3)2-doped and MnCO3-doped CaCO3 are 0.27 and 0.24 respectively after 100cycles, compared with the conversion of 0.16 for original one after the same number of cycles. Compared with calcined original CaCO3, better pore structure is kept for calcined Mn-doped CaCO3 during calcium looping cycle. The pore volume of calcined MnCO3-doped CaCO3 is 2.4 times as high as that of calcined original CaCO3 after 20cycles. The pores of calcined MnCO3-doped CaCO3 in the pore size range of 27–142nm are more abundant relative to clacined original one. That is why modification by manganese salts can improve cyclic CO2 capture capacity of CaCO3. [Copyright &y& Elsevier]

Abstract: This paper examines the average carbonation conversion, CO2 capture efficiency and energy requirement for post-combustion CO2 capture system during the modified calcium-based sorbent looping cycle. The limestone modified with acetic acid solution, i.e. calcium acetate is taken as an example of the modified calcium-based sorbents. The modified limestone exhibits much higher average carbonation conversion than the natural sorbent under the same condition. The CO2 capture efficiency increases with the sorbent flow ratios. Compared with the natural limestone, much less makeup mass flow of the recycled and the fresh sorbent is needed for the system when using the modified limestone at the same CO2 capture efficiency. Achieving 0.95 of CO2 capture efficiency without sulfation, 272kJ/mol CO2 is required in the calciner for the natural limestone, whereas only 223kJ/mol CO2 for the modified sorbent. The modified limestone possesses greater advantages in CO2 capture efficiency and energy consumption than the natural sorbent. When the sulfation and carbonation of the sorbents take place simultaneously, more energy is required. It is significantly necessary to remove SO2 from the flue gas before it enters the carbonator in order to reduce energy consumption in the calciner. [Copyright &y& Elsevier]

• NO is efficiently removed by CO in carbonation of Mn-doped CaO in calcium looping. • MnO in Mn-doped CaO efficiently catalyzes NO removal by CO in carbonation. • Mn promotes CO 2 capture by CaO in fluidization state. • Mn is a bi-function additive for simultaneous NO/CO 2 removal by CO and Mn-doped CaO. • NO removal and CO 2 capture efficiencies reach 99% and 85%, respectively. By utilizing CO as NO reductant and CaO as the catalyst, NO removal by CO can be realized in the carbonation stage of calcium looping for CO 2 capture, but the carbonation of CaO decreases the catalytic effect on NO removal. To realize efficient and stable NO removal in the carbonation stage, CaO was modified by Mn in this work. NO removal performance of CO in the carbonation stage of Mn-doped CaO in the calcium looping process was investigated in a bubbling fluidized bed reactor. In the carbonation stage, NO removal efficiency sharply increases from 0% to 99% and CO 2 capture efficiency increases from 73% to 88% due to the presence of Mn. Compared with CaO, Mn-doped CaO possesses a stronger catalysis on NO removal by CO and higher CO 2 capture capacity. MnO in Mn-doped CaO is an excellent and stable catalyst for NO removal by CO, which greatly mitigates the negative effect of the carbonation and the sintering of CaO on NO removal. The molar ratio of Mn/Ca = 3.5:100 is recommended. To achieve efficient NO removal and CO 2 capture in the carbonation stage of Mn-doped CaO, CO concentration in the range of 3000–4000 ppm and carbonation temperature of 650 °C are recommended. Under severe calcination conditions (950 °C and 80% CO 2), CO 2 capture and NO removal efficiencies reach 85% and 99% in 10 cycles, respectively. The periodic density functional theory calculations show that the catalytic active sites for NO removal by CO are changed from O-tops to Mn-tops in Mn-doped CaO, so the adsorptions of NO and CO 2 are greatly enhanced, promoting the subsequent simultaneous NO removal and CO 2 capture. Thus, Mn is a bi-functional additive to promote CO 2 capture by CaO and catalyze NO removal by CO. Mn-doped CaO seems promising for efficient simultaneous NO removal and CO 2 capture in the carbonation stage of the calcium looping process. [ABSTRACT FROM AUTHOR]

Calcium looping uses CaO carbonation/calcination cycles to capture CO 2 , which is a promising carbon capture technology for coal-fired power plants. However, after CaO absorbs CO 2 to generate CaCO 3 , the catalytic performance of CaO for NO x reduction by CO decreases drastically. In this work, Mn-doped CaO was used to improve NO reduction by CO in carbonation of calcium looping and the mechanism of Mn-doped CaO on NO reduction by CO was determined by the density functional theory. The experimental results show that Mn doping not only improves the CO 2 capture capacity of CaO, but also increases NO reduction by CO. Density functional theory calculation results show that the Mn atom provides new adsorption sites for CO and NO on CaO surface, respectively. After addition of Mn, the values of co-adsorption energy for CO and NO on CaO surface increases by 1.5 and 6.9 times in the carbonation stage, respectively. In addition, the total energy barrier for the reaction of NO reduction by CO under the catalysis of CaO in carbonation stage decreases from 11.08 to 8.66 eV due to the addition of Mn. The negative effect of the carbonation of CaO on NO removal by CO is greatly mitigated by Mn. Therefore, NO removal by CO in the presence of Mn-doped CaO is significantly improved in the carbonation stage of the calcium looping. [Display omitted] • Effect of Mn-doped CaO on NO-CO reaction in calcium looping was studied by DFT. • Mn significantly catalyzes NO removal by CO in carbonation stage of calcium looping. • Mn changes reaction paths and the adsorption sites of NO and CO in presence of CaO. • Mn decreases energy barriers of NO reduction reaction by CO from 11.08 to 8.66 eV. [ABSTRACT FROM AUTHOR]

• Novel SiC/Mn co-doped CaO pellets are prepared for calcium looping heat storage. • Co-doped pellets show good heat storage capacity in multiple heat storage cycles. • Optical and thermal capacities of pellets rise by 16.6 and 2.2 times, respectively. • Co-doped pellets exhibit high crushing strength and attrition resistance in cycles. To achieve high heat storage capacity, excellent mechanical, optical and thermal properties in calcium looping thermochemical heat storage, the novel SiC/Mn co-doped CaO pellets were fabricated by the extrusion-spheronization method. The heat storage performances of the novel CaO pellets were studied under harsh calcination (pure CO 2 , 950 °C) and pressurized carbonation (pure CO 2 , 13 bar, 800 °C) conditions in a dual fixed-bed reactor system. The additions of SiC and Mn enhance the cyclic stability of CaO pellets during the multiple heat storage cycles. When the mass ratio of CaO:SiC:MnO 2 is 100:5:5, the co-doped CaO pellets exhibit an excellent heat storage performance. The effective conversion and heat storage density of the co-doped CaO pellets are 41.5% higher than those of original CaO pellets, respectively. Meanwhile, the co-doped CaO pellets possess a good optical absorption capacity and a high thermal conductivity, which are 17.6 and 3.2 times as high as those of original CaO pellets, respectively. In addition, the co-doped CaO pellets show much higher crushing strength and lower weight loss during the attrition test. The stronger interaction between SiC and CaO cluster mitigates the movement of CaO, which is determined by density functional theory simulation. The adsorption of CO 2 onto the CaO surface is enhanced by the addition of Mn. Therefore, SiC/Mn co-doped CaO pellets used in the calcium looping thermochemical heat storage process appear promising. [ABSTRACT FROM AUTHOR]

• Effect of Cu on NO-char reaction in carbonator of calcium looping is studied by DFT. • Density of state result proves that Cu-char keeps stable NO removal ability in CaL. • Cu reduces energy barriers of NO reduction by char and CO. • Cu changes reaction paths and the order of absorbed reactants and released products. • Char shows a higher NO reduction activity than CO in the presence of Cu. Cu can improve NO removal efficiency of char and CO in carbonation stage of calcium looping, but the mechanism of NO reduction by char and CO in the presence of Cu has been rarely reported. In this work, the density functional theory was utilized to investigate the effect of Cu on NO reduction by both char and CO in carbonation stage of calcium looping for CO 2 capture. Density of state result proves that Cu decreases the possibility of char deactivation and retains stable promoting effect for NO reduction. Adsorption energies and structural parameters were used to determine adsorption sites of reactant molecules (CO, NO and O 2) and Cu atom on the basic configuration of zigzag graphite structure with six benzene rings. Adsorption energies of reactant molecules on char surface in the presence of Cu follow the order: CO < NO < O 2. Cu decreases energy barriers for NO reduction by char, NO reduction by CO and CO oxidation by O 2 from 31.73, 61.31, 113.86 kcal/mol to 19.99, 12.51, −11.68 kcal/mol, respectively. Accordingly, Gibbs free energies reduce from 1.14, −7.69, −66.02 kcal/mol to −39.95, −9.21, −68.10 kcal/mol, respectively. Therefore, Cu significantly promotes NO reduction by both char and CO as well as CO oxidization by O 2. Furthermore, char has more significant effects on the reduction of NO than CO in the presence of Cu. Thus, the effect of Cu on reaction paths is determined. [ABSTRACT FROM AUTHOR]

• Simultaneous NO/CO 2 removal by Cu-modified biochar/CaO in calcium looping is proposed. • Cu strongly catalyzes NO removal by biochar and CO in carbonator of calcium looping. • CaO not only catalyzes NO removal by CO but also absorbs CO 2 in carbonator. • 90% NO and 80% CO 2 are removed by Cu-modified biochar/CaO. A novel method to realize the simultaneous NO/CO 2 removal by Cu-modified biochar and CaO in the carbonation stage of calcium looping was proposed. Cu-modified biochar was added in the carbonation stage as a NO reductant, meanwhile CaO was added as a CO 2 sorbent. The simultaneous NO/CO 2 removal performance of Cu-modified coconut shell char/CaO in the carbonation stage of calcium looping was investigated in a bubbling fluidized bed reactor. CO is generated by the oxidation of the coconut shell char in the presence of O 2 in the carbonation. Cu-modified biochar and the generated CO efficiently reduce NO. Cu in Cu-modified biochar shows a strong catalysis on NO reduction by both char and CO. Besides, Cu enhances the conversion of CO to CO 2 , which is absorbed by CaO. CaO also catalyzes NO removal by CO, but the catalytic effect gradually becomes weak as the carbonation proceeds. When Cu content in Cu-modified coconut shell char is 0.77%, mass ratio of Cu-modified biochar to CaO is 1:16 and O 2 concentration is 3%, NO removal and CO 2 capture efficiencies of Cu-modified biochar/CaO in the carbonator are 94% and 80% at 650 °C, respectively. To reach the same NO removal efficiency of 94% in the carbonator, the required addition amount of Cu-modified biochar is only approximately 20% of untreated biochar. [ABSTRACT FROM AUTHOR]

• Simultaneous NO/CO 2 removal system using biochar/CaO in calcium looping is proposed. • Coconut shell char/limestone shows good simultaneous NO/CO 2 removal performance. • CaO shows a strong catalysis effect on NO reduction by CO produced by char oxidation. • Porous structure of biochar enhances NO reduction under calcium looping conditions. • NO removal and CO 2 capture efficiencies are above 97% and 80%, respectively. A novel simultaneous NO/CO 2 removal system using biochar and calcined limestone in the calcium looping process was proposed. Coconut shell char and calcined limestone were added into a carbonator in the calcium looping process as the NO reductant and CO 2 sorbent, respectively. The simultaneous NO/CO 2 removal performance of coconut shell char/calcined limestone in the calcium looping process was investigated in a bubbling fluidized bed reactor. NO and CO 2 in flue gases are effectively and simultaneously removed by coconut shell char/calcined limestone in the presence of O 2. O 2 plays an important role in NO removal by coconut shell char. The calcined limestone shows a strong catalytic effect on NO reduction by CO generated by the reaction of coconut shell char and O 2. The calcined limestone supports active sites for NO reduction by CO. High CO concentrations and high carbonation temperatures have positive effects on NO reduction by CO with calcined limestone catalysis. However, the catalytic effect of calcined limestone is weakened by its carbonation, which is promoted by the high temperature and additional CO 2 produced by the oxidation of char. The simultaneous NO removal and CO 2 capture efficiencies can reach above 97% and 80%, respectively. The porous structure of coconut shell char is an important factor in enhancing NO reduction with calcined limestone catalysis in the presence of O 2. [ABSTRACT FROM AUTHOR]

Abstract Extracellular proteases are often produced as pre-pro-enzyme and then undergo multiple processing steps to mature into the active form. The protease Epp, a virulent factor of Vibrio anguillarum, belongs to this family. Its maturation might be regulated by Ca2+ via its polycystic kidney disease (PKD) domain, but the molecular mechanism is unknown. Herein, we report the crystal structure of the first PKD domain from V. anguillarum Epp (Epp-PKD1) and its specific Ca2+-binding capacity. Epp-PKD1 exists as a monomer, consisting of seven β-strands which form two β-sheets stacking with each other. One Ca2+ is bound by the residues Asn3, Gln4, Asp27, Asp29, Asp68 and a water molecule with a pentagonal bipyramidal geometry. Incubating the apo Epp-PKD1 with Ca2+ but not Mg2+, Mn2+, or Zn2+, enhances the thermal and chemical stability of Epp-PKD1, indicating its specific binding to Ca2+. Epp-PKD1 shares high similarity in both sequence and overall structure with that of Vibrio cholerae PrtV, a homologous protease of Epp, however, they differ in the oligomeric state and local structure at the Ca2+-binding site, suggesting maturation of PrtV and Epp might be differently regulated by Ca2+. Likely, proteases may take advantage of the structural diversity in PKD domains to tune their Ca2+-regulated maturation process. Highlights • Crystal structure of the first PKD domain of Vibrio anguillarum Epp is determined. • Epp-PKD1 contains a pentagonal-bipyramidal Ca2+-binding site. • Specific binding to Ca2+ increases conformational stability of Epp-PKD1. • Epp-PKD1 differs in the oligomeric state and Ca2+ coordination from the homologous PrtV-PKD1. [ABSTRACT FROM AUTHOR]

A Ca 3 Al 2 O 6 -stabilized carbide slag from calcium looping cycles for CO 2 capture was proposed as a H 2 S sorbent in zero emission carbon process. The H 2 S removal performance of Ca 3 Al 2 O 6 -stabilized carbide slag experienced different calcium looping cycles was investigated in a muti-fixed-bed reactor. The fabricated sorbent containing the mass ratio of CaO to Ca 3 Al 2 O 6 = 73:27 shows higher CO 2 capture capacity. The sulfidation temperature and H 2 S concentration exhibit the important effects on H 2 S removal by the fabricated sorbent from CO 2 capture cycles. The number of CO 2 capture cycles has a little effect on H 2 S removal by the fabricated sorbent. The sulfidation conversions of the fabricated sorbent after 100 CO 2 capture cycles at 60 and 120 min can reach 1.3 and 1.6 times as high as those of carbide slag, respectively. Ca 3 Al 2 O 6 restrains the rapid growth of CaO grains in the fabricated sorbent in CO 2 capture cycles. Compared with carbide slag, the fabricated sorbent possesses larger surface area and more stable structure during CO 2 capture cycles because of the support of Ca 3 Al 2 O 6 , so it exhibits higher sulfidation conversion. H 2 S removal using Ca 3 Al 2 O 6 -stabilized carbide slag from calcium looping cycles seems promising in zero emission carbon process. • C3A-modified carbide slag has high CO 2 uptake and stability in multiple CaL cycles. • The modified carbide slag after CO 2 capture cycles shows excellent H 2 S uptake. • C3A improves CO 2 and H 2 S removal capacities of carbide slag from CaL cycles. • CO 2 capture and H 2 S removal by modified carbide slag can be realized in ZEC process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu/Ce-modified CaO greatly enhances NO reduction by CO in CaL CO 2 capture process. • Cu/Ce interaction promotes oxygen vacancies and surface oxygen generation on CaO. • Cu/Ce modification improves the co-adsorption of CO/NO/CO 2 on CaO. • 99 % NO reduction at low molar ratio of CO/NO = 2 in CaL process is achieved. • 99 % CO conversion is achieved during NO reduction process. In the calcium looping CO 2 capture process, using CO in the flue gas to reduce NO at a high molar ratio of CO to NO (e.g., above 10:1) can achieve efficient removal of NO. However, the lots of unreacted CO causes secondary pollution. In this study, a novel Cu/Ce co-modified CaO was proposed for cyclic CO 2 capture and the catalytic NO reduction at a low CO:NO molar ratio (e.g., 2:1). The experimental findings indicate that Cu/Ce modification improves the performance of CaO in both catalytic NO reduction and carbonation. The Cu/Ce co-modified CaO contained the optimal Cu/Ce/Ca molar ratio of 1:5:100 possesses both NO removal and CO conversion efficiencies of above 99 %, along with CO 2 removal efficiency exceeding 88%. Microscopic analysis determines that the electron transfer between Cu and Ce facilitates the conversion of lattice oxygen into surface oxygen, mitigating the competition between CO 2 and CO for surface oxygen. Furthermore, density functional theory calculations demonstrate that CO/NO/CO 2 exhibits non-competitive adsorption behavior on Cu/Ce co-modified CaO. Consequently, Cu/Ce-modified CaO possesses superior catalysis for efficient NO reduction by CO at low CO:NO molar ratio in calcium looping process. [ABSTRACT FROM AUTHOR]

Abstract: This study focuses on enhancing CO2 uptake by modifying limestone with acetate solutions under pressurized carbonation condition. The multicycle tests were carried out in an atmospheric calcination/pressurized carbonation reactor system at different temperatures and pressures. The pore structure characteristics (BET and BJH) were measured as a supplement to the reaction studies. Compared with the raw limestone, the modified sorbent showed a great improvement in CO2 uptake at the same reaction condition. The highest CO2 uptake was obtained at 700°C and 0.5MPa, by 88.5% increase over the limestone at 0.1MPa after 10cycles. The structure characteristics of the sorbents on N2 absorption and SEM confirm that compared with the modified sorbent, the effective pores of limestone are greatly driven off by sintering, which hinders the easy access of CO2 molecules to the unreacted-active sites of CaO. The morphological and structural properties of the modified sorbent did not reveal significant differences after multiple cycles. This would explain its superior performance of CO2 uptake under pressurized carbonation. Even after 10cycles, the modified sorbent still achieved a CO2 uptake of 0.88. [Copyright &y& Elsevier]